The protection of wood exposed in aquatic and terrestrial environments has long posed a challenge. For centuries, marine borers were a major cause of deterioration of wooden ships and the economic well being of seafaring nations depended upon their ability to maintain a sea-worthy fleet. While wooden ships no longer play a major role in maritime commerce, wood forms an important component of the marine infrastructure, particularly in underdeveloped countries. In the developed countries, wooden ships, pilings, and buildings are important components of authentic reconstruction of historical towns and fishing villages. Wood used in these exposures is typically treated with high levels of preservatives that can include creosote, chromated copper arsenate, or ammoniacal copper zinc arsenate. While these chemicals are very effective, concerns have arisen about the potential for their migration into the surrounding water column and the effect on non-target marine organisms. There remains a public demand for the development of less toxic marine wood treatments.
Similarly, degradation of wood in terrestrial environments by the action of termites and other insects has been met by use of lumber pressure treated with many of the above agents, including arsenates. Contamination of soils and fresh water supplies from leaching from pressure treated lumber is an environmental concern.
One problem with developing alternative treatments is a lack of knowledge about how the current treatments affect various marine borers and terrestrial insects. This lack of knowledge stems from the widespread effectiveness of the chemicals currently used for this purpose, which has up to now suppressed development of commercially economic, environmentally safer alternatives. Aquatic wood protection, and wood protection in general, has tended to develop by increasing the amount of preservative to achieve a toxic threshold, then further increasing the preservative or treatment to ensure that most of the treated wood achieves this level of protection. This approach results in little concern for the effects of the toxicant on the target organism. Applicants found that the development of alternative control strategies for marine environments can be accomplished by a more intimate knowledge of marine borer biology.
Teredinid bivalves (shipworms) are important degraders of wood in marine environments. Unlike other marine wood borers, shipworms use wood as a food source, but they do so via symbiotic cellulolytic nitrogen fixing bacteria. Waterbury, et al. A cellulolytic nitrogen-fixing bacterium cultured from the Gland of De shayes in shipworms(Bivalvia: Tereinidae), 221 Science 1401 (1983). The role of these bacteria in shipworm biology, particularly as it relates to substrate selection, remains poorly understood. Similarly, termites use a flagellated protozoan (genus Trichonympha) as symbiont.
The invention discloses tests to identify inhibitors of a symbiont cellulolytic organism and to identify new compounds for wood treatment to limit or prevent degradation, preferably compounds that have fewer environmental problems that those presently used.